1. Field of the Invention
This invention relates to a drive chain cover for use on a toning station employed in electrophotographic printers and copiers. More particularly, this invention relates to a drive chain cover assembly used to protect the toning station drive chain from contact with toner, which may cause damage to the drive chain, resulting in shortened useful chain life.
2. Brief Description of the Related Art
Throughout this disclosure, the term xe2x80x9celectrophotographic printerxe2x80x9d is to be construed to include printers and copiers employing electrophotographic means for image production. Electrophotographic printers that utilize a dry ink toner-based developer include a toning station having a toning shell that is used to transport the developer mix to an image development area where the toner is applied to a photoconductor that carries an electrostatic image. The toner interacts electrostatically with the photoconductor, temporarily bonding to the photoconductor before being transferred to the paper.
Typically, the toning shell is driven by means of a chain driven by a sprocket affixed to a shaft that ultimately is driven through gear box actuated by the main drive of the copier. Such drive chains are typically made of polymeric material, encasing pins that contact the cogs on the drive sprockets. In order to maintain appropriate chain tension, it is important that the drive chain remain flexible. However, contact with toner can damage the polymeric materials from which the drive chains are constructed, causing the chain to stiffen, dramatically limiting its usefulness and shortening the useful life of the chain, requiring its early replacement. Unfortunately, the drive chains necessarily reside in an environment in which contact with toner is a high probability. Although the toner is contained in a large toner reservoir, toner may be spilled by the printer operator when replacing the toner reservoir, and such spilled toner falls directly onto the drive chains. Additionally, during normal operation of the equipment, toner dust migrates from the development area of the printer, driven by air currents created by moving parts of the equipment. Thus, toner dust naturally migrates out of the image development area and into the open areas of the toning station, ultimately contacting the drive chains. Modifications to the toning station to minimize the amount of toner spillage and migration may be expensive and not feasible, given space constraints inside the printer.
Additionally, many toning stations open, with an upper portion pivoting away from a lower portion about a hinge joint, to allow for cleaning and maintenance of the toning station components. Any device used to protect the chains from contact with toner dust must therefore be compatible with opening the toning station, by physically permitting the upper portion of the station to pivot with respect to the lower portion of the station, and by not dumping accumulated toner dust onto the drive chains when the toning station is opened. Therefore, there is a need in the art for an improved means of protecting the drive chains from contact with toner dust.
The present invention solves these and other shortcomings of the prior art by including a flexible chain guard that covers the main toning station drive chain, shielding the chain from toner spills and directing the toner away from the chain when the toning station is opened. The flexible chain guard also works in conjunction with a rigid, fixed chain guard to shield the drive chains and drive sprockets from excessive toner dust contamination.
One embodiment of the present invention is an electrophotographic printer that includes a toning station having a rotating toning shell driven by at least one drive chain. A photoconductor is located in close proximity to the toning shell, defining an image development area therebetween. A flexible drive chain cover is located adjacent the image development area.
In another embodiment, at least a portion of the flexible drive chain cover is substantially planar, and includes a seal area located immediately adjacent the image development area, the seal area made from a fibrous material, such as felt, and engaging the photoconductor to reduce toner migration out of the image development area.
In a further embodiment, the electrophotographic printer also includes a rigid drive chain cover located adjacent the flexible drive chain cover, such that the rigid and flexible drive chain covers overlap. The rigid drive chain cover may be located on a toner replenisher assembly located adjacent the toning station.
In a further embodiment, the toning station includes an upper portion and a lower portion, connected by a hinge, the upper portion pivoting on the hinge to separate from the lower portion to provide access to the lower portion. The flexible drive chain cover is located adjacent the drive chain and remains adjacent the drive chain when the upper portion of the toning station is pivoted with respect to the lower portion of the toning station. The flexible drive chain cover flexes to allow the upper portion of the toning station to pivot with respect to the lower portion of the toning station.